System and method for expansion of field of view in a vision system

Abstract

This invention provides a field of view expander (FOVE) removably attached to a vision system camera having an image sensor defining an image plane. In an embodiment the FOVE includes first and second mirrors that transmit light from a scene in respective first and second partial fields of view along first and second optical axes. Third and fourth mirrors respectively receive reflected light from the first and second mirrors. The third and fourth mirrors reflect the received light onto the image plane in a first strip and a second strip adjacent to the first strip. The first and second optical axes are approximately parallel and a first focused optical path length between the scene and the image plane and a second focused optical path between the image plane and the scene are approximately equal in length. The optical path can be rotated at a right angle in embodiments.

What is claimed is: 
     
       1. A system for expanding a field of view of a scene imaged by a vision system camera assembly having an image sensor, the system being constructed and arranged to search and analyze features of interest in the scene comprising:
 a first outer mirror oriented at an acute angle with respect to an optical axis of the vision system camera assembly and a second outer mirror oriented at an opposing acute angle with respect to an opposing side of the optical axis; and 
 a beam splitter located forward of the first outer mirror and the second outer mirror in a direction taken from the vision system camera assembly, the beam splitter including a first reflecting surface and a second reflecting surface wherein the first outer mirror and first reflecting surface are arranged to direct a first field of view from the scene along the optical axis to the image sensor and the second outer mirror and second reflecting surface are arranged to direct a second field of view from the scene along the optical axis to the image sensor, 
 wherein the first field of view is at least in part separated from the second field of view at the scene along a horizontal direction, and 
 wherein the first outer mirror, the second outer mirror and the beam splitter are arranged to project each of the first field of view and the second field of view in a horizontally stacked relationship of strips towards the image sensor, wherein the optical axis is approximately parallel to a plane of said scene imaged by the vision system camera assembly. 
 
     
     
       2. The system as set forth in  claim 1 , wherein the camera assembly is oriented with 90 degrees rotation about the optical axis to provide a vertically stacked relationship of the strips at the image sensor. 
     
     
       3. The system as set forth in  claim 1  wherein the camera assembly is oriented to provide a horizontally stacked relationship of the strips at the image sensor. 
     
     
       4. The system as set forth in  claim 3  wherein the first reflecting surface and the second reflecting surface define a vertically oriented v-shape centered through the optical axis. 
     
     
       5. The system as set forth in  claim 1  wherein the first field of view and the second field of view overlap by a predetermined overlap distance along the horizontal direction. 
     
     
       6. The system as set forth in  claim 5  wherein the predetermined overlap distance is at least as large as a largest feature of interest along the horizontal direction to be searched by the vision system camera assembly. 
     
     
       7. The system as set forth in  claim 6  wherein the feature of interest is a symbology code, the system further comprising a symbology code decoding system that receives information related to located symbology codes from the vision system camera assembly and outputs code data to a further interconnected process. 
     
     
       8. The system as set forth in  claim 7 , wherein the symbology code is located on an object moving on a conveyor through the scene, and optionally further wherein the symbology code comprises a one-dimensional barcode approximately oriented in the horizontal direction on an object. 
     
     
       9. The system as set forth in  claim 1  wherein the image sensor defines a predetermined M (width)×N (height) pixel resolution that compresses a roughly square geometry. 
     
     
       10. The system as set forth in  claim 9 , wherein the M (width)×N (height) pixel resolution defines at least one of 1024×768 pixels, 2048×384 pixels and 2048×768 pixels. 
     
     
       11. A method for expanding a field of view of a scene imaged by a vision system camera assembly of a vision system, the camera having an image sensor, and the system being constructed and arranged to search and analyze features of interest in the scene, comprising the steps of:
 directing light from the scene through a first outer mirror oriented at an acute angle with respect to an optical axis of the vision system camera assembly and a second outer mirror oriented at an opposing acute angle with respect to an opposing side of the optical axis; and 
 with a beam splitter located forward of the first outer mirror and the second outer mirror in a direction taken from the vision system camera assembly, the beam splitter including a first reflecting surface and a second reflecting surface, projecting a first field of view from the scene through the first outer mirror, to the first reflecting surface, and then along the optical axis to the image sensor and projecting a second field of view from the scene through the second outer mirror, to the second reflecting surface, and then along the optical axis to the image sensor, 
 wherein the step of projecting the first field of view and the step of projecting the second field of view includes separating the first field of view at least in part from the second field of view relative to the scene along a horizontal direction, and projecting a horizontally stacked relationship of strips that respectively define the first field of view and the second field of view towards the image sensor, wherein the optical axis is approximately parallel to a plane of said scene imaged by the vision system camera assembly. 
 
     
     
       12. The method as set forth in  claim 11  wherein the step of separating first field of view and the second field of view overlap by a predetermined overlap distance along the horizontal direction. 
     
     
       13. The method as set forth in  claim 12 , wherein the predetermined overlap distance is at least as large as a largest feature of interest along the horizontal direction to be searched by the vision system camera assembly. 
     
     
       14. The method as set forth in  claim 11 , further comprising, with a vision system application, searching and analyzing an overall image from the image sensor, and locating from the overall image, the features of interest therein free of stitching together image information from the strips. 
     
     
       15. The method as set forth in  claim 11 , wherein the features of interest comprise symbology codes located on an object moving relative to the scene. 
     
     
       16. The method as set forth in  claim 15  wherein at least one of the symbology codes comprises a one-dimensional-type barcode oriented to extend approximately along the horizontal direction.